Meghan was born and raised in Nantucket, Massachusetts, the daughter of Gary and Kelly Trainor. She is married to actor Daryl Sabara.

Meghan grew up in a musical family, and has been writing songs since she was eleven years old. When she was thirteen, her parents bought her a computer so that she could produce her own songs. The family later moved to Hyannis, MA so that Trainor and her two brothers, Ryan and Justin, could attend Nauset Regional High School in nearby North Eastham.

Meghan’s mother is of one half French-Canadian, one quarter Polish, and one quarter Irish, descent; she also has remote English and Guernsey [Channel Islander] ancestry on her French-Canadian side.

Meghan’s maternal grandfather is Thomas Ramon Jekanowski, Jr. (the son of Thomas Ramon Jekanowski and Mary R. O’Donnell). Meghan’s grandfather Thomas was born in Massachusetts. Meghan’s great-grandfather Thomas was of Polish origin, and was the son of Piotr “Peter” Jekanowski and Valeria/Waleria Lewandoska. Mary R. was of entirely or almost entirely Irish descent, and was the daughter of Patrick Sarsfield O’Donnell and Katherine M. Riley.

Meghan’s maternal grandmother is Jeanne Marie LaPalm (the daughter of Joseph Lawrence Lapalm and Jeanette E. Poudrier). Meghan’s grandmother Jeanne was born in Massachusetts. Lawrence was the son of Horace Louis Lapalm and Albertine LaPrade, both of whom were the children of French-Canadian parents. Meghan’s great-grandmother Jeanette was also of French-Canadian origin, the daughter of Elzear Joseph Poudrier and Corina/Corrine Raymond. Megan’s grandmother’s ancestry also includes remote English and Guernsey [Channel Islander].